protected ProviderInternal<? extends T> getDefaultConvention() {
        return Cast.uncheckedCast(NOT_DEFINED);
    }

    @Override
    protected boolean isDefaultConvention() {
        return getConventionSupplier() == NOT_DEFINED;
    }

    @Override
    protected String describeContents() {

        // context serves as a token here to ensure that the scope is opened.
        return value;
    }

    protected S getConventionSupplier() {
        return state.convention();
    }

    protected final String describeValue() {
        return value.toString();
    }

        setToConventionIfUnset();
        action.execute(getConfigurer(true));
    }

    @Override
    protected boolean isDefaultConvention() {
        return isNoValueSupplier(getConventionSupplier());
    }

    private boolean isNoValueSupplier(CollectionSupplier<T, C> valueSupplier) {
        // Cannot use plain NoValueSupplier because of Java restrictions:

    @Override
    protected MapSupplier<K, V> getDefaultConvention() {
        return noValueSupplier();
    }

    @Override
    protected boolean isDefaultConvention() {
        return isNoValueSupplier(getConventionSupplier());
    }

    private MapSupplier<K, V> emptySupplier() {
        return new EmptySupplier();
    }

    private MapSupplier<K, V> noValueSupplier() {